A professional childminder who shook an 11-month old baby girl so violently that her neck "snapped back and forth" was found guilty of manslaughter yesterday.

Keran Henderson, 43, had been looking after Maeve Sheppard at her Buckinghamshire home in March 2005 when she lost her temper. The court heard that the registered childminder then shook the baby, causing her to lose consciousness. Maeve was rushed to hospital with brain injuries, but died a few days later.

Yesterday the baby's parents, Ruth and Mark Sheppard, said they had done everything possible to ensure their baby would be safe with Henderson.

"We carried out the relevant checks to make sure Keran was a good, trustworthy childminder and our gut instinct was to trust her," they said in a statement.

"It was purely a professional relationship and if only she had told us that it was not working out between her and Maeve then we would have our baby daughter with us today."

Henderson, who ran her childminding business from her home at Iver Heath, Buckinghamshire, denied shaking the baby, claiming the 11-month-old had a seizure while having her nappy changed.

But yesterday a jury at Reading crown court found the mother-of-two guilty by a majority of 10 to two.

The judge, Mr Justice Keith, sentencing Henderson to three years in prison, said: "Mr and Mrs Sheppard trusted you to look after Maeve. We do not know what really happened to make you snap in the way the jury found that you did."

Henderson's family, including husband Iain, reacted angrily to the verdict and proceedings were halted. When they resumed, Henderson again broke down and had to be helped from the dock.

Earlier, the court had heard that the 43-year-old had been hired by the Sheppards in January 2005 on the recommendation of a friend. Maeve was the couple's first child and Sheppard told the court that she had agonised about going back to work at the end of her maternity leave.

"I was a bit split on how I felt about going back to work," she said. "Half of me wanted to stay at home and the other half of me knew that we had to work and we didn't know if we could survive on one wage with a new baby."

Henderson had seven years' caring experience and was a popular and well respected childminder. When Sheppard met her, the jury heard she had a long list of questions, but added that Henderson had answered them all.

"I was quite happy with the arrangements," said Sheppard. "It was very well-ordered house, she had a schedule and a routine, it was clean and tidy and we got on very well."

Henderson told the court that the baby had been ill almost from the first day she was in her care, a claim Maeve's parents denied. She said that on the day Maeve was rushed to hospital her body had "stiffened and jerked back" as Henderson changed her nappy.

She said the baby's eyes had rolled back into her head, her body went floppy and she was gurgling as if something was stuck in her throat.

The baby's neck ligaments were "over-extended", indicating her neck had snapped back and forth. Expert witnesses for the defence said this could have happened days, weeks or even months beforehand. Experts for the prosecution said they could only have been caused by violent shaking.

The court heard that on the morning of March 2 2005 emergency services had come to Henderson's home and Maeve was taken to hospital. Doctors fought to save her but her condition deteriorated. Her life support machine was turned off two days later.

In the days following the baby's death Henderson gave up her childminding career. "I wasn't able to look after the children," she said. "I was basically curled up in a ball on the settee, shaking and crying, in total shock."

The court had been due to hear a victim impact statement from Sheppard yesterday but following the disruption in court the judge changed his mind, telling the couple that he had read their statement in private and digested its contents.

He then told Henderson: "Your reputation as someone who parents can confidently leave their children with has been shattered ... You are going to have to live the rest of your life with the knowledge that Maeve died in your care."

In a statement Maeve's parents welcomed the verdict, adding they felt no animosity to Henderson's family. "We will never be able to forgive this woman for what she took away from us. Now the trial has finally come to an end, we can start to think about moving on with our lives - but nothing can bring back our baby that we loved with all our hearts."